VLISP also provides functions to inspect a reactor definition from within an application program, or at the Console prompt:
$ (vlr-type circleReactor)
:VLR-Object-Reactor
$ (vlr-data circleReactor)
"Circle Reactor"
You can use this data to distinguish among multiple reactors that can fire the same callback function.
_$ (vlr-owners circleReactor)
(#<VLA-OBJECT IAcadCircle 03ad077c>)
$ (vlr-reactions circleReactor)
((:vlr-modified . PRINT-RADIUS))